Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$162.77	7.802%	$175.4693	$175.47	$175.45	$175.50
Purchase #2	$133.57	5.612%	$141.0659	$141.07	$141.05	$141.10
Purchase #3	$226.40	8.488%	$245.6168	$245.62	$245.60	$245.60
Purchase #4	$55.51	6.696%	$59.2269	$59.23	$59.25	$59.20
Purchase #5	$138.92	4.428%	$145.0714	$145.07	$145.05	$145.10
Purchase #6	$121.31	13.654%	$137.8737	$137.87	$137.85	$137.90
Purchase #7	$72.64	13.408%	$82.3796	$82.38	$82.40	$82.40
7 purchase totals =	$911.12		$986.7036	$986.71	$986.65	$986.80